Up to now, a corrugated fin is employed as a fin for a heat exchanger, and multiple louvers are cut in and raised from a surface of the corrugated fin along an air flowing direction. A technique in which a heat exchanging performance is improved by changing specifications such as a width of the corrugated fin, fin pitches, or a length of the louvers has been variously proposed (for example, refer to Patent Document 1).
Incidentally, in the fin for the heat exchanger having the multiple louvers, when the louver pitches are miniaturized to increase the number of louvers, a heat transfer coefficient of the fin is improved by a tip effect of the louvers, and a heat transfer performance can be improved. In recent years, with an advance of manufacturing techniques, the louver pitches can be miniaturized more than conventional manufacturing limitation dimensions.
However, when the louver pitches are miniaturized, although the heat transfer coefficient is improved, the fin efficiency is reduced, and a heat flow rate emitted from the fin is reduced. This leads to a case in which as a real fin, an improvement in the heat transfer performance attributable to the miniaturization of the louver pitches cannot be sufficiently obtained. That is, in the heat exchanger fin having the multiple louvers, it is difficult to improve the heat transfer performance by merely miniaturizing the louver pitches.